Alpha-1-antitrypsin (AAT) is an alpha-1-globulin present in serum and various other body fluids. As synthesized in the liver, mature AAT is a glycoprotein having a molecular weight of about 50,000 to 55,000 daltons. Proteolytic enzymes inhibited by AAT include trypsin, chymotrypsin, pancreatic elastase, skin collagenase, renin and urokinase, as well as proteases of polymorphonuclear lymphocytes. Genetically acquired deficiency of AAT in humans is associated with various pathological conditions, especially emphysema and liver disease. See, for example, Morse, N. Eng. J. Med. 299 (19):1045-1048 (1978) and 299 (20):1099-1105 (1978); Tobin et al., Arch. Int. Med. 143 (7):1342-1348 (1982); and Carrell et al., Nature 298 (5872):329-334 (1982).
Elastase is a proteinase which breaks down lung tissue. Unchecked, its activity can result in emphysema. Gadek et al., Am. Rev. Respir. Dis. 127:S45 (1983) and Glaser et al., Am. Rev. Respir. Dis. 127:547-553 (1983), for example, have shown that AAT can be therapeutically useful in treatment of emphysema.
Because of its therapeutic utility and because comparatively large amounts are required for certain indications, such as replacement therapy for patients genetically deficient in AAT, researchers have been looking for techniques to produce AAT in large quantities. Conventionally such techniques have involved purification of AAT from blood plasma.
Recent efforts have focused on production of AAT in transformed microorganisms or cells, especially E. coli and yeast, due to the promise of such techniques to produce large quantities of engineered gene products. Several researchers have reported success in such endeavors. However, a practical process for purifying such recombinant AAT is useful in pharmaceutical applications is not available.
It is an object of the present invention to provide an improved process for purifying AAT from serum or from recombinant microorganisms, yeasts or cells, especially from recombinant bacteria and yeasts, which is capable of performance at large scale.
Laurell et al., J. Chromatog. 278:53-61 (1983) describe use of thiol-disulfide exchange chromatography to isolate AAT.